Vitamin D is often called the sunshine vitamin, because your skin makes it when sunlight falls on it. It helps the body absorb calcium, keeps bones and muscles working properly, and supports the immune system. The problem is that large numbers of people, especially in countries with long, dark winters, run low on it without realising, because the signs are vague and easy to blame on modern life. This guide explains the common signs, who is most at risk, and what to do if you suspect a problem.
The Common Signs of Low Vitamin D
The most reported sign is tiredness that sleep does not fix: a flat, heavy fatigue that lingers through the day. Alongside it, many people notice aching bones and muscles, a dull pain in the lower back or legs, and muscles that feel weaker than they should, making stairs and shopping bags harder work than they used to be.
Low mood is another frequent companion. Vitamin D and mood are linked in ways researchers are still mapping out, but feeling unusually low through the winter months is a pattern doctors hear often. Other possible signs include catching infections more often than usual, wounds and cuts healing slowly, and in some people, more hair shedding than normal.
In children, severe deficiency can soften growing bones, a condition called rickets. In adults, long-term severe deficiency can soften bones too, causing deep aches and weakness. These serious forms are less common, but they are the reason deficiency is worth taking seriously rather than shrugging off.
Why the Signs Are Easy to Miss
Almost every sign on that list has a dozen other possible causes. Tiredness, aches and low mood could be stress, poor sleep, too little exercise or half a dozen illnesses. That overlap is exactly why vitamin D deficiency slips past people for months, and why guessing is pointless: the only reliable way to know your level is a blood test, which a doctor can arrange if your symptoms and risk factors suggest it.
Who Is Most at Risk?
Anyone whose skin rarely sees the sun. People in northern countries get little useful sunlight for vitamin D between about October and March, because the sun sits too low. People who work night shifts, stay indoors most of the day, or cover their skin for cultural or personal reasons make less. Darker skin needs more sun exposure to make the same amount, so deficiency is more common in people with brown or black skin living far from the equator. Older skin also produces vitamin D less efficiently, and some gut conditions reduce how well the body absorbs it from food and supplements.
Where Vitamin D Comes From
Sunlight is the main source for most people in the brighter months: short periods outside with some skin uncovered, taking care never to burn. A daily walk does double duty here, and our guide to what happens when you walk 30 minutes every day covers the wider benefits.
Food contributes a smaller share. Oily fish such as salmon, mackerel and sardines are the richest natural source, with smaller amounts in egg yolks, red meat and foods with vitamin D added, such as some breakfast cereals and spreads. Our beginner’s guide to a balanced diet shows where these foods sit in ordinary eating. Because food and winter sun often fall short together, health services in the UK suggest that everyone considers a daily supplement of 10 micrograms during autumn and winter, and that people at higher risk consider one all year round.
If several signs in this article sound familiar, do not self-diagnose and do not take large doses on your own. Ask for a blood test, and treat a confirmed deficiency with the dose your doctor recommends, then let the follow-up test prove it worked.
This article is general information only and is not medical advice. If you think you may have a vitamin deficiency or any of the symptoms described, please speak to a qualified health professional.
